There is a known art pertaining to a spark-ignition internal combustion engine in which vibration intensity changing patterns in multiple frequency ranges are extracted from a signal picked up by a knock sensor in a predetermined knock determination period, and it is determined that knock is occurring if the number of vibration intensity changing patterns in frequency ranges that rise at the same timing among the vibration intensity patterns in the plurality of frequency ranges is equal to or larger than a threshold (see, for example, Patent Literature 1).
Patent Literature 2 describes a technology in which a knock determination period and a noise determination period are set, effects of noise on a signal picked up by the aforementioned knock sensor are determined based on the signal picked up during the aforementioned noise determination period, and the determination as to the occurrence of knocking that is made based on the aforementioned picked-up signal during the aforementioned knock determination period is suspended based on the result of determination.
Patent Literature 3 describes a technology of estimating the intensity of knock from the rise time and the fall time of a knock signal output by a knock sensor.